1. Field of the Invention
This invention relates to a full rotary loop taker assembly for sewing machines, and more particularly to a full rotary loop taker assembly of the type in which the rotatable loop taker is rotated as it receives rotation from a driver driven for rotation around an axis which intersects the rotative axis of said loop taker.
2. Description of the Prior Art
A prior art which is of interest to this invention is disclosed in U.S. Pat. No. 2,219,470, entitled "Shuttle Mechanism," published Oct. 29, 1940 and granted to Carlson. In this prior art, the loop taker or shuttle is supported for rotation around a first rotative axis by a shuttle support. On the other hand, a driver for imparting rotation to the shuttle is driven for rotation around a second rotative axis which intersects the first rotative axis. The driver is provided with two diametrically opposed projections, while the shuttle is provided with two diametrically opposed engaging holes or slots, said slots being adapted to respectively receive the projections on the driver.
In such arrangement, when the driver is rotated, two projections are alternately received in the corresponding engaging holes, whereby the shuttle is rotated. That is, immediately before one projection escapes from the corresponding engaging hole, the other projection enters the corresponding engaging hole, so that the shuttle is continuously rotated at a uniform speed. In addition, such rotation of the shuttle is effected in synchronism with the reciprocating motion of the sewing needle.
Thus, the shuttle mechanism disclosed in U.S. Pat. No. 2,219,470 is arranged so that the two projections alternately enter the respective corresponding holes to drive the shaft for rotation; but it has the following problem. This problem stems from the fact that immediately before one projection escapes from the corresponding engaging hole, the other projection enters the corresponding engaging hole but that the degree of this entry is very low. When the shuttle arresting the upper thread loop draws said upper thread loop, it is subjected to a resistance, from this upper thread, opposite to the direction of rotation. Therefore, the rotation of the shuttle sometimes fails to proceed as desired, and the projection, which should ordinarily enter the corresponding engaging hole, tends to go under the bottom surface of the shuttle. Nevertheless, the driver is rotatively driven, with the result that the projection applies an upward force to the shuttle. As this time, since the shuttle is held down by a cover which closes the shuttle support, a strong frictional force is produced between the shuttle and the cover, making it impossible for the shuttle to rotate smoothly.